The larger town next to mine has monthly tours of their wastewater and water processing plants. Although they’re scheduled to be amenable for K-12 student field trips, they also see adults who wish to understand how their tax dollars are being expensed for the public good.

For other municipal services, you might also reach out to the director of that department, since as public servants, they can also schedule special tours of the facilities for members of the public. It can’t hurt to ask.